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It's not about learning Python (syntax) but presents you small and fun riddles. Solving the riddles is based on Python but you can use whatever fits (your calculator, bash scripts, Perl...). After you solved one, you get to see how others have solved it and can discuss the pros & cons of the different ways.

Very nice to get a feel for how things could be done (smart) in Python. This site works especially well if you know a bit about other scripting languages or the commandline, etc.

Welcome to Google's Python Class --
this is a free class for people with a
little bit of programming experience
who want to learn Python. The class
includes written materials, lecture
videos, and lots of code exercises to
practice Python coding. These
materials are used within Google to
introduce Python to people who have
just a little programming experience.
The first exercises work on basic
Python concepts like strings and
lists, building up to the later
exercises which are full programs
dealing with text files, processes,
and http connections. The class is
geared for people who have a little
bit of programming experience in some
language, enough to know what a
"variable" or "if statement" is.
Beyond that, you do not need to be an
expert programmer to use this
material.

I first ran across Software Carpentry looking at lists of python tutorials.. but its a lot more than a tutorial on python. turns out what I really learned was how to use subversion, and that none of my projects are better suited to python than to perl... yet.